KNOW THE GAMS

Some gems are more expensive than others, sometimes depending on rarity and other times on demand or fashion. A good emerald easily costs more than a diamond, while a turquoise costs '. because emeralds are rarer than diamonds and diamonds are rarer than most turquoise.

Yet if rarity were the only gauge of a precious gem, the Australia black opal would be among the most precious, if not the most precious, gems. Although diamonds are found in many countries, black also are found only in Australia. As late as the middle of 1978, no black opals had been found for years. They were ex. rare-and still are, despite the major find in September, 1978 which resulted in an "opal rush" of miners and gem merchant. Among a reputed $500,000 worth of opals dug by a single miner was one gem estimated to be worth a record $90,000.

As far as fashion and demand go, they can be capricious. India and in Roman times, diamonds were the most desirable gem. During the Middle Ages in Europe, the most highly esteemed gems were the colored stones. According to goldsmith Benvenuto Celleni, sapphires, and diamonds-in that order-were the most precious stones in sixteenth-century Italy. During that same time in Portugal, it was emeralds, rubies, and diamonds. Today, diamonds head the list.

Fashion, in fact, can inflate the cost of any gem. In the Victorian Age, jet was popular, especially for mourning jewelry because of Queen Victoria's addiction to it after the death of Prince Albert. At the same time, cat's-eye chrysoberyl was in demand following the Duke of Connaught's gift of an engagement ring with that stone to Princess Louise Margaret of Prussia. In short, any time a gem is in demand, the price rises; when it is not in demand, the price, although it still may be high, is lower than at other times.

"Expensive," "rare," and "precious," therefore, are not always synonyms. Most jewelers and experts today, in fact, veer away from categorizing gems as precious and semiprecious, despite the traditional and general distinction of diamonds, emeralds, rubies, sapphires, and some opals as being precious and all other stones semiprecious.